textproduct: Quad Cities

KEY MESSAGES

- A cold front will bring low chances (10-20%) for showers and storms early this morning with isolated storms possible (20-30%) this afternoon along and south of Highway 34.

- An active pattern is in store next week as multiple rounds of showers and storms are likely through Friday. Currently, the greatest severe potential is Monday evening when the SPC has a Slight Risk, Level 2 out of 5, for our northwestern counties.

SHORT TERM /THROUGH SUNDAY NIGHT/

Issued at 1222 AM CDT Sat Sep 12 2026

Storm chances return today as a cold front moves into the area from the northwest. During the morning hours, isolated showers and storms (10-20% coverage) will form along the front across eastern Iowa before fizzling out once they reach the Mississippi River as low-level WAA weakens during the afternoon and the wind shifts from southwesterly to northwesterly. There is some disagreement among CAMs on a possible second round of convection forming over southwestern Iowa and moving eastward with a subtle shortwave in the zonal flow, but current HREF guidance only has a 10-20% chance of this occurring. If any storms do redevelop, frontal placement will also be key in determining the severe potential along and south of Highway 34 as there is going to be a short window where the 250-500 J/kg of SBCAPE and 25-30 knot 0-6-km bulk shear overlap.

Heading into tonight, the cold front pushes into northern Missouri and central Illinois before stalling out, and a weak high pressure positions itself over the Dakotas and Minnesota. Winds will shift to northeasterly as lows drop into mid-50s to low 60s. By Sunday, a longwave ridge builds across the Northern Rockies as another shortwave trough swings into the Great Lakes region. A Front Range low is expected to develop in Colorado in response, enabling a mid-level F-gen band to develop over Iowa on the north side of the stationary front as a stratiform rain shield forms with isolated lightning. There will be a break in the rain heading into Sunday night before storms redevelop Monday morning as the upper level flow becomes southwesterly, converting the stationary front into a warm front.

LONG TERM /MONDAY THROUGH FRIDAY/

Issued at 1222 AM CDT Sat Sep 12 2026

Monday-Tuesday...The longwave ridge over the Northern Rockies shifts eastward over the Mid-to-Upper Mississippi Valley as a closed heights center replaces it over the Northern Rockies. Diffluent flow aloft and strong low-level WAA should support storms (50-80% coverage) along the warm front in eastern Iowa, but limited moisture, especially near the surface, will put a hamper on the coverage (20-40%) across west-central and northwest Illinois. Regardless, the southerly return flow behind the warm front is forecasted to allow dew points to climb back into the upper 60s and low 70s along the cold front diving southeastward as the trough over the Northern Rockies lifts into south-central Canada. After another dry period Monday afternoon, storms will once again redevelop Monday evening along the approaching cold front where a 40-knot LLJ is expected to enhance the low-level shear. Current LREF guidance has the sfc-to-500 mb wind shear vector oriented at a 45-degree angle and close to 35 knots which would suggest a mixed convective mode. However, by the time any convection reaches our CWA, it will likely be in the form of linear clusters, promoting a more damaging wind threat. This is why the SPC already has a Slight Risk, Level 2 out of 5, for severe storms Monday night in our northwestern counties.

By Tuesday, the storms are expected to decrease in intensity along the front as upper-level dynamical support is lost. A weak high pressure is forecasted to slide into Minnesota Tuesday night, reinforcing the northeasterly flow over the CWA and pinning the stationary front in our south. This stationary front will act as the focal point for showers and storms through the middle of next week.

Wednesday-Friday...The entire area will be sandwiched between a ridge over the Southeast and a positively tilted trough over Hudson Bay that extends back towards the Pacific Northwest. This pattern should support diffluent flow aloft over the residual stationary front as rounds of stratiform rain and storms develop along it on Wednesday and Thursday. As the Southeast ridge retrogrades westward, the flow is forecasted to return to a more stable zonal flow as the boundary begins to wash out Friday without any major air mass changes. By the end of the next week though, there is a good chance (50-80%) that areas across eastern Iowa and northwest Illinois will see over 2 inches of rainfall with swaths of 4+ inches possible (20-30%).

AVIATION /06Z TAFS THROUGH 06Z SUNDAY/

Issued at 1209 AM CDT Sat Sep 12 2026

The main concern over the next 24 hours is a cold frontal passage with a wind shift out of the south to northwest. With this front, expect SCT low and upper-level clouds, but general VFR conditions are expected outside a brief period of BKN MVFR ceilings along the front. These cloud will also help suppress widespread fog, but there is a small chance (20-30%) that MVFR visibilities could develop at any site around or after daybreak. In terms of precipitation chances, PoPs are 20% or below for all TAF sites which led to the exclusion of any PROB30s at this issuance. If any site would receive precipitation, it would be briefly this morning at CID and this afternoon at BRL.

DVN WATCHES/WARNINGS/ADVISORIES

IA...None. IL...None. MO...None.